645464021 has 2 divisors, whose sum is σ = 645464022. Its totient is φ = 645464020.

The previous prime is 645464011. The next prime is 645464047. The reversal of 645464021 is 120464546.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 598047025 + 47416996 = 24455^2 + 6886^2 .

It is a cyclic number.

It is not a de Polignac number, because 645464021 - 2²⁶ = 578355157 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645464011) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322732010 + 322732011.

It is an arithmetic number, because the mean of its divisors is an integer number (322732011).

Almost surely, 2^645464021 is an apocalyptic number.

It is an amenable number.

645464021 is a deficient number, since it is larger than the sum of its proper divisors (1).

645464021 is an equidigital number, since it uses as much as digits as its factorization.

645464021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 23040, while the sum is 32.

The square root of 645464021 is about 25405.9839604767. The cubic root of 645464021 is about 864.2194038171.

The spelling of 645464021 in words is "six hundred forty-five million, four hundred sixty-four thousand, twenty-one".